Butter. We bake, so we keep salted and unsalted in the freezer. (I know, I know, only barbarians salt their butter). Anyhow, 4 sticks is 1 lb. Package weight (unlike canned goods) is negligible. So once the scale is balanced, all you do is remove one of the butter packages back to the freezer, and fill the bucket with feed till it balances again. Measure that volume, and you have your pound of "whatever". Or just mark the bucket and always fill to that line.
I had been thinking to balance the scale with two of anything, then use it to weigh equal portions of each food, then measure the volume of each food portion. Then use that volume of one food, and 9 times that volume of the other food.
But your way sounds even better, because it lets you measure the volume of food that has a known weight of one pound.
I hadn't thought of butter before, so thank you for pointing it out. I usually have plenty of it in my freezer, too